Question

In this exercise, you will compare the amino acid sequence from the aphid to the amino acid sequences of the other species to identify how similar they are. As a first step, you will compare the aphid sequence (Acyrthosiphon) to a bacterial sequence (Pantoea).

The sequences below show the first 60 amino acids of one polypeptide, using the one-letter abbreviations for the amino acids. An underscore (_) indicates a gap inserted in a sequence to optimize its alignment with the corresponding sequence in Arabidopsis.
Acyrthosiphon (aphid) IKIIIIGSGV GGTAAAARLS KKGFQVEVYE KNSYNGGRCS IIR_HNGHRF DQGPSL__YL
Pantoea (bacterium) KRTFVIGAGF GGLALAIRLQ AAGIATTVLE QHDKPGGRAY VWQ_DQGFTF DAGPTV__IT
At how many positions are the amino acids the same between the two species?

Answer 1

Upon comparison, the Acyrthosiphon (aphid) and Pantoea (bacterium) amino acid sequences are identical at 8 positions out of the first 60 in their polypeptide chains, indicating some level of similarity between the two species.

Step-by-step explanation:

In the realm of molecular biology, comparing the amino acid sequences of proteins from different species is a common method to determine evolutionary relatedness and functional similarity. To answer the student's question, we must count the number of positions at which the amino acids in the aphid's protein sequence are identical to those in the bacterial protein sequence.

Upon comparing the provided sequences for Acyrthosiphon (aphid) and Pantoea (bacterium), we can see that they share the following amino acids at the same positions: I at positions 1, V at position 11, G at positions 16 and 25, A at positions 17 and 23, L at position 22, R at position 24, and F at position 53.

This results in a total of 8 identical amino acid positions out of the first 60 in the polypeptide sequences. Comparisons like this can reveal degrees of similarity between species and infer evolutionary relationships, akin to the conclusions drawn from cytochrome c amino acid sequence comparisons in various organisms stated in the example.